"We fear up to 50 (dead). We understand it is a vehicle bomb," said the official

Saul Perlmutter and Adam Riess of the US and Brian Schmidt of Australia will divide the prize.
The trio studied what are called Type 1a supernovae, determining that more distant objects seem to move faster.
Their observations suggest that not only is the Universe expanding, its expansion is relentlessly speeding up.
Prof Perlmutter of the University of California, Berkeley, has been awarded half the 10m Swedish krona (£940,000) prize, with Prof Schmidt of the Australian National University and Prof Riess of Johns Hopkins University's Space Telescope Science Institute sharing the other half.
'Weak knees' Prof Schmidt spoke to the Nobel commitee from Australia during the ceremony.
"It feels like when my children were born," he said.
"I feel weak at the knees, very excited and somewhat amazed by the situation. It's been a pretty exciting last half hour."
The trio's findings form the basis of our current understanding of the Universe's origins, but raises a number of difficult questions.
In order to explain the rising expansion, cosmologists have suggested the existence of what is known as dark energy. Although its properties and nature remain mysterious, the predominant theory holds that dark energy makes up some three-quarters of the Universe.
Their goal was to measure distant Type 1a supernovae - the brilliant ends of a particular kind of dense star known as a white dwarf.
Because their explosive ends are of roughly the same brightness, the amount of light observed from the supernovae on Earth should be an indication of their distance; slight shifts in their colour indicate how fast they are moving.
At the time, the competing teams expected to find that the more distant supernovae were slowing down, relative to those nearer - a decline of the expansion of the Universe that began with the Big Bang.
Instead, both teams found the same thing: distant supernovas were in fact speeding up, suggesting that the Universe is destined for an ever-increasing expansion.
What the trio found has sparked a new epoch in cosmology, seeking to understand what is driving the expansion.
Commenting on the prize, Prof Sir Peter Knight, head of the UK's Institute of Physics, said: "The recipients of today's award are at the frontier of modern astrophysics and have triggered an enormous amount of research on dark energy."
"These researchers have opened our eyes to the true nature of our Universe," he added. "They are very well-deserved recipients."
The Nobel prizes have been given out annually since 1901, covering the fields of medicine, physics, chemistry, literature and peace.
Monday's award of the 2011 prize for physiology or medicine went to Bruce Beutler of the US, Jules Hoffmann from France and Ralph Steinman from Canada for their work on immunology.
This year's chemistry prize will be announced on Wednesday.

Tokelau declared a state of emergency late on Monday, following a similar move in neighbouring Tuvalu, where water is already being rationed.
A New Zealand-administered territory of three islands, Tokelau's 1,400 people have less than a week's drinking water left.
The lack of rainfall is blamed on the La Nina weather pattern.
Officials said Tokelau had run out of natural fresh water and was relying solely on bottled water.
New Zealand Foreign Minister Murray McCully said other islands in the South Pacific were also reporting water shortages.
Parts of Samoa have begun rationing water.
He said New Zealand was rushing to assess the situation throughout the region, amid fears the crisis could escalate.
A New Zealand Air Force plane landed in Tuvalu on Monday carrying containers of water and desalination units.
Tuvalu, one of the world's smallest independent nations, with a population of about 11,000, lies about halfway between Australia and Hawaii. Tokelau is about 500km (310 miles) to the east.
Impact on crops Mr McCully said the situation was urgent in parts of Tuvalu.
He said there was less than a week's supply of drinking water on Funafuti, the main island of Tuvalu.
"I understand one of the other outlying islands, Nukulaelae, has a more urgent shortage and there is a desalination plant on the way there," Mr McCully said.
"There are going to be some flow-on effects here, clearly this is having a severe impact on crops, so there's likely to be a food shortage as well."
La Nina causes extreme weather, including both drought and floods, and was blamed for floods in Australia, South East Asia and South America in late 2010 and early 2011.
David Hebblethwaite, a water conservation expert with the Secretariat of the Pacific Community, said Tuvalu had experienced low rainfall for the past three years and there had been no precipitation at all for seven months.
He said Funafuti and Nukulaelae both lacked groundwater supplies, making them dependent on rainfall collected from the roofs of homes and government buildings.
Mr Hebblethwaite said the islands may also need extra medical supplies if water shortages lead to sanitation issues and consequent health problems.

The warning followed media reports that a group of activists had been filmed, insulted and attacked in Paris.
Earlier, an Amnesty International report accused Syria of a campaign of intimidation against activists abroad.
It quoted the activists as saying that Syrian embassy staff had threatened them and their relatives in Syria.
Meanwhile, Russia has said it will not support a draft resolution condemning Syria's suppression of pro-democracy protests, which is to be put to the UN Security Council on Tuesday.
'Systematically harassed' French foreign ministry spokesman Bernard Valero, quoted by Agence France-Presse, said Syrian activists had been given more police protection in the wake of the alleged intimidation, which is now being investigated.

"The right to protest freely and peacefully in safety is fully guaranteed by the French constitution, and it is also obvious that France supports the Syrian people's hopes for freedom."
Le Monde newspaper had reported an attack on a small group of Syrian protesters in a square in central Paris.
In its report entitled Syria: The long reach of the Mukhabaraat, Amnesty International details the cases of 30 Syrian activists in eight countries, in Europe and North and South America, who have been systematically monitored and harassed by Syrian embassy officials and others believed to be acting on behalf of the Syrian regime.
The report says the dissidents' relatives in Syria have also, in some cases, apparently been exposed to harassment, detention and even torture. Some activists say they were directly threatened by embassy officials.
Naima Darwish, who set up a Facebook page to call for protests outside the Syrian embassy in Santiago, Chile, told Amnesty she was contacted directly by a senior official who asked to meet her in person.
"He told me that I should not to do such things. He said I would lose the right to return to Syria if I continued."
Amnesty has called on host countries to take stronger action against the Syrian embassies accused of orchestrating the intimidation campaign.
Robert Ford, the US ambassador in Syria, also renewed criticism of the Syrian government, calling on it to stop its "incredible repression" and allow a political process of transition to move forward peacefully.
Import ban rescinded Meanwhile, Russia said it would not support Tuesday's UN draft resolution.
Deputy Foreign Minister Gennady Gatilov said that Moscow "cannot support a text" that did not urge other countries not to become involved in Syria's internal affairs.
But it is unclear whether Moscow will veto the resolution.
On Tuesday, Turkish media reported that a colonel who had defected from the Syrian army was calling for a united front against Mr Assad.
"Opponent forces in Syria should get united and close ranks until the regime collapses," Col Riad al-Asaad, who is sheltering in Turkey, told the Anatolia news agency.
Separately, Syria has withdrawn a ban it imposed on many consumer goods and raw materials, amid reported discontent over rising prices.
The ban was intended to preserve foreign currency reserves.
Syria is under international pressure to stop using force to suppress protests that began six months ago.
The UN estimates that more than 2,700 people have been killed across Syria since the crackdown began.
On Tuesday the Syrian Observatory for Human Rights said three soldiers and one civilian had been killed in fighting between government troops and army defectors in the Jabal al-Zawiya region in north-west Syria.
The government says it is in the process of introducing reforms and is speaking to members of the opposition - it blames the unrest on armed gangs.

Speaking after an Italian court cleared Amanda Knox and Raffaele Sollecito of murder, Meredith's brother Lyle said it felt like it was "back to square one".
Italian prosecutors say they will appeal. Only Rudy Guede, 24, has been convicted for Miss Kercher's murder.
Knox has since left Italy and is on her way back to the US.
She is travelling back to her hometown of Seattle on a commercial flight and is expected to land at around 0100 BST on Wednesday (0000 GMT, 1700 PDT on Tuesday).
Speaking to reporters in Perugia, where his sister was studying at the time of her death, Mr Kercher said: "We accept the decision and respect the court and the Italian justice system.
"We do find we are now left looking at this again and thinking how a decision that was so certain two years ago has been so emphatically overturned, which raises other questions.
"It feels very much like back to square one. The search goes on to find out what really happened."
During a separate earlier trial, Guede was convicted of Miss Kercher's murder and sentenced to 30 years in prison. On appeal, his conviction was upheld but his sentence reduced to 16 years.
It was said in court that Guede did not act alone - raising questions following the acquittals as to who had also been at the murder scene.
Meredith's sister, Stephanie, said the "biggest disappointment" was still not knowing what happened and knowing "someone or people out there" were responsible.
"It's still very difficult to speak in terms of forgiveness," she added.
"Until the truth comes out, we can't forgive anyone because no-one's even admitted to it knowing there was someone out there who was responsible."

"Of something so terrible happening, when basically she was in the safest place, her bedroom."
Prosecutors said Miss Kercher was killed in a brutal sex game which went wrong.
Mrs Kercher admitted she could appreciate why Knox would feel she had lost her life over the last few years.
"I don't think anyone's going to get off scot-free," she said. "Their lives have been disrupted - no-one is untouched by this."
Earlier, UK Prime Minister David Cameron said he felt sympathy for the Kerchers.
"They previously had an explanation about what happened to their daughter and they don't have that any more, and I think all of us should be thinking of them," he said.
'Nightmare over' Knox, 24, and Mr Sollecito, 27, spent nearly four years in jail but their convictions were overturned on Monday after evidence was found to be unreliable.
The prosecution is to appeal to Italy's highest court, although it appears unlikely that Knox would be extradited back to Italy from the US.
An eight-member jury cleared both defendants of Miss Kercher's murder after doubts were raised over procedures used to gather DNA evidence.
The judge upheld Knox's conviction for slander for accusing bar owner Patrick Diya Lumumba of carrying out the killing. But he set the sentence at three years, time that Knox has already served, meaning she was free to leave.
She was ordered to pay him 22,000 euros (£18,800) in compensation.
Her family said she had "suffered for four years for a crime she did not commit".
Speaking on the steps of the court, Knox's sister Deanna said: "We are thankful to the court for having the courage to look for the truth and to overturn this conviction."
She said her sister's "nightmare was over" and asked for privacy for her family to recover from "this horrible ordeal".
Knox's lawyer, Carlo Della Vedova, said outside court that there was "no winner" in the case and the appeal court had "rectified a mistake".
"Meredith was a friend of Amanda - we should never forget this and we have to respect the sorrow of all the families," he told the BBC.
Mr Sollecito's father Francesco said he had "allowed himself some tears" following the verdict and said the court had "given me back my son".
Hundreds of people had gathered in the streets outside the court ahead of the verdict and some shouted "shame" when they heard about the decision, while others cheered.

Eyewitnesses said a truck carrying explosives was driven into a gate near a government ministry and detonated.
A spokesman for the Islamist militant group al-Shabab told the BBC it had carried out the attack.
It is the largest attack since al-Shabab withdrew its forces from Mogadishu in August.
Rescue workers said more than 50 people had been injured in the blast. Many of the victims were soldiers and students who had been waiting at the education ministry.
The UN-backed transitional government condemned the attack and said no senior government officials were hurt in the blast. Government members were meeting in the building near the blast site at the time.
"The attack shows that the danger from terrorists is not yet over and that there are obviously still people who want to derail the advances that the Somali people have made towards peace," it said in a statement.
The government statement set the number of dead at 15, but it was not clear whether this was only an initial count.
'Walls fell apart' The blast struck outside a compound housing government buildings in Kilometre Four (K4) - a crossroads in central Mogadishu.
Police officer Ali Hussein told the Associated Press news agency that the vehicle had exploded after pulling up at a checkpoint on the way into the official compound.

"All of a sudden a huge, huge sound and all the furniture and all the windows and all the walls started falling apart," he said.
The vehicle carrying the explosives was big, he said, about an eight- or 10-tonne truck.
"The building that has been destroyed houses eight ministries, and you can imagine how crowded it would have been."
He said the area was protected, "but unfortunately, it was not good enough".
"Almost half of the cabinet sit in that building. So you can understand it was a good target for them - the terrorists."
BBC Somali's Mohammed Dhore in Mogadishu said vehicles were on fire, bodies lying in the street and shocked soldiers were randomly firing into the air in the aftermath.
Our correspondent said it was the worst incident he had ever come across.
One aid worker said the force of the blast had thrown body parts hundreds of metres away.

Ali Abdullahi, a nurse at Medina hospital in the city, said victims were being brought in with horrific wounds, including burns and lost limbs. Some had been blinded, he said.
"It is the most awful tragedy I have ever seen," he told AP.
"Dozens are being brought here minute-by-minute. Most of the wounded people are unconscious and others have their faces blackened by smoke and heat."
Famine crisis Somalia has been without an effective central government since 1991 - the weak transitional government and Islamist militias are competing for control of the country.
It retreated from Mogadishu two months ago following an offensive by African Union troops,, but analysts had predicted that without a front line, the organisation was likely to begin carrying out more bombings, including suicide attacks.
Last week, al-Shabab tried but failed to seize two towns from pro-government forces near Somalia's border with Kenya.
Somalia's political instability has been compounded in the past year by the worst drought in six decades, which has forced tens of thousands of people to flee to Mogadishu in search of food.
The UN has declared a famine in six regions of Somalia.
The BBC's East Africa correspondent, Will Ross, said the latest attack will not only worry the government, but also the aid agencies, who have been taking great risks to get food to the drought victims.

The comments, made during a ceremony south of the capital, come a week after Field Marshal Tantawi testified in secret at the former president's trial.
Mr Mubarak is charged with the killing of protesters during the 18-day revolt which forced him from office.
Some 850 demonstrators were killed.
"The armed forces fight for Egypt and not for just anyone, whoever it may be," said Field Marshal Tantawi, who served as defence minister under Mr Mubarak for 20 years.
"I testified before God and I told the truth," he said.
Media blackout "Nobody asked us to open fire and nobody will open fire" on the people, he added.
A strict media blackout was imposed before Field Marshal Tantawi's appearance at Mr Mubarak's trial on 24 September.
His testimony was seen as vital in the trial where the former president faces charges of ordering government forces to fire on protesters. Mr Mubarak, who denies the charges, could face the death penalty if found guilty.
During the session, lawyers representing some of those people killed complained Field Marshal Tantawi gave evidence earlier than usual and left the courthouse without allowing them to cross-examine him.
Field Marshal Tantawi was initially set to testify earlier in the month, but failed to attend the session citing a busy schedule and instead offering to submit a written testimony - raising opposition suspicions that he was deliberately foot-dragging.
The BBC's arab affairs editor Sebastian Usher says protesters demanding swifter democratic reform have complained that Field Marshal Tantawi is being too soft on his former boss.
Mr Mubarak's security chief Habib al-Adli and six top police officers are also on trial with the former leader. About 100 other police officers charged with using deadly force are on trial separately around the country.

 
He said Israel should restart peace talks with the Palestinians and restore good relations with Turkey and Egypt.
Mr Panetta spoke while travelling to the region for talks with Israeli and Palestinian leaders.
Diplomatic efforts have intensified recently to push the two sides back to peace talks that were abandoned last year.
Israel has agreed to participate in such talks, but the Palestinians want Israel to stop building more homes for settlers in the occupied territories.
Israel announced last week it planned to build 1,100 more homes in a settlement in occupied East Jerusalem
"It's pretty clear, at this dramatic time in the Middle East when there have been so many changes, that it is not a good situation for Israel to become increasingly isolated. And this is what has happened," Mr Panetta told journalists aboard a US Air Force plane en route to the Middle East.
He is due to have meetings with Israeli Prime Minister Benjamin Netanyahu and Defence Minister Ehud Barak.
Mr Panetta said the US would make sure Israel maintained its military superiority in the region, but should use this advantage to press for peace.
"As they take risks for peace, we will be able to provide the security that they will need in order to ensure that they can have the room hopefully to negotiate," he said.
No 'slam-dunk' Mr Panetta is also due to meet with Palestinian Authority President Mahmoud Abbas and Prime Minister Salam Fayyad.
The US opposes the Palestinian bid for full membership of the United Nations. Washington has threatened to veto the move if it comes to a vote in the Security Council, saying negotiations should resume to a two-state solution.
Mr Panetta said he would press the Palestinians to return to peace talks.
"The most important thing they can do is go to the negotiating table. You are not going to achieve Middle East peace by trying to slam-dunk it at the UN," he said.
Mr Abbas presented a formal request to the UN asking for membership of a Palestinian state in the West Bank, Gaza Strip and East Jerusalem, based on the 1967 borders.
Israel captured these Palestinian territories in the 1967 war and still occupies the West Bank and East Jerusalem.

Eyewitnesses said about 150 people raided the village of Lingyado, in Zamfara state close to the border with Niger, with guns and machetes.
A police spokesman said it appeared to be a reprisal attack in response to a similar incident in August.
Security forces have been sent to the area to restore order.
Police spokesman Sunusi Amiru said six others were wounded in the attack and were receiving medical attention.
"We are on top of the situation, we are on the trail of the suspects, we have deployed more men to the trouble spots," he told Reuters news agency.
The BBC's Nigeria correspondent Jonah Fisher says the victims were attacked as they emerged from their homes.
When the shooting began, some residents fled into nearby cornfields, the Associated Press news agency reports.
Some of the attackers shouted that they would rape any women they found, one witness, Ahmad Tsauri Lingyado, told AP.
One witness, speaking from hospital, told the BBC that his house was targeted first, and that he saw both his grand-daughter and daughter-in-law killed.

Knox, 24, and Raffaele Sollecito, 27, are challenging their convictions for killing Miss Kercher, 21, from south London, in Perugia, Italy, in 2007.
The verdict is expected on Monday after final statements from the pair, who were jailed for 26 and 25 years.
Prosecutors have said they will appeal if the verdict is overturned.
The appeal case has centred on a review of DNA evidence on a kitchen knife, thought to be the murder weapon, which indicated it was flawed.
But prosecutors called for the sentences to be increased to life terms, saying there was also considerable circumstantial evidence putting the ex-lovers at the scene of the killing.
Final statements The trial has heard some colourful phrases used to describe Knox, with one lawyer comparing the American to Who Framed Roger Rabbit cartoon character Jessica Rabbit, and another to a witch.
Carlo Pacelli, who represents Diya "Patrick" Lumumba, who Knox originally accused of the murder - she says under pressure from the police - said she had a split personality.
The jury, which comprises two judges and six members of the public, will retire to consider its verdict after the statements.
If the conviction is upheld, the pair can appeal for a final time at Italy's highest appeals court.
Knox's family have said they will take her back to Seattle immediately if it is overturned, despite prosecutors vowing to appeal.
Miss Kercher, from Coulsdon, had been sharing a cottage with Knox during an exchange year abroad from Leeds University.
Prosecutors says she was killed in a brutal sex game which had gone wrong. Her throat had been slit and she had been sexually assaulted.
Miss Kercher's family have said they feel the true victim has been "completely forgotten", with the media's focus on Knox.
In a recent interview on Italian television, her sister Stephanie said: "In these four years, Meredith has been completely forgotten. But we need to find justice for her, we need to find the truth for her."
Knox was sentenced to 26 years in prison, while her former Italian boyfriend Sollecito was given 25 years. Both deny any wrongdoing.
A third person - Rudy Guede, 21 - was also convicted of Miss Kercher's murder in a separate trial and was sentenced to 30 years in prison.
His conviction was upheld on appeal but reduced to 16 years.

The village is connected to mainland Greece by a ferry. Years ago, when I first came to the island, there were three ferries a week in each direction.
Now there is one, but the cabins are clean, the food is good and the 18-hour journey gives the opportunity to meet fellow travellers and renew acquaintances with fellow villagers.
Except for August, the ship is sparsely occupied and when I came out in late September I was soon talking to Dimitris, a port policeman coming back from leave in Athens.
Public servants are much abused these days and often blamed for the crisis in Europe. There are five port police in my village and it is easy to caricature them as expensive and unnecessary.
However, we are close to Turkey, a major route for drug- and people-smuggling. There is the ferry boat to oversee, and even if they are nearly empty, the daily tourist boats that come from the south of the island have to be attended to.
Dimitris's wife and children live in Athens and he tries to get to see them every six weeks for a long weekend, but the irregular ferry schedule makes this difficult.
Working-class Greeks are happy to talk about their finances and Dimitris told me he had been earning 1,500 euros a month (£1,300, $2,000). I asked about the "had been", and he told me the government had cut the salary of all public servants.
His pay, he said, had been reduced by 230 euros a month and from October this would be reduced by a further 70 euros.
I wondered what would happen in Britain or Germany if the police had their pay arbitrarily cut by close to £300 a month.
And I wonder how much tax take the government lost by cutting public-sector salaries and how much the shops have lost as money is taken from the pockets of the population.
State of limbo Greece applies a strict supply-and-demand model to higher education and there is much competition for the few university places.
In return for a college education, schoolteachers and doctors agree to spend their first year in remote rural places and in the islands.
Of course, the doctors are extraordinarily young and so were the teachers, but that is changing.
There are no jobs on the mainland for last year's teachers and so they have to spend another year in the village teaching the children of shepherds and fishermen, labourers and stonemasons.
Another year away from friends and family, another year before marriage and children.
The state of limbo is unlikely to nurture a feeling of gratitude towards the government of the day as it struggles to alleviate the effects of corruption and mismanagement by its predecessors.
A further blow is a sudden emergency property tax, based on size, and householders in the village have received one-off bills for 400 euros and more.
A cruel twist is that the government is collecting this tax via the state-controlled electricity company. The threat is: If you do not pay, your electricity will be cut off.
The electricity company does not like tax collecting, nor do its employees, and the villagers are saying they will not pay.
If they really do join protesters who refuse to pay motorway tolls this tax strike could drag Greece into an unstructured default and nobody knows where that would lead.
If a government cannot gather taxes, it cannot govern.
Tourist trickle Life is not cheap in Greece. I recently paid 42 euros for 18 litres of petrol for my small boat, which makes it expensive to go fishing.
A 250-gram packet of butter costs in excess of five euros at the nearest supermarket some 40km (25 miles) away.
The sudden hike in the price of milk and butter will lead to more goats in the village and a return to eating drilla, the thick sour cream extracted from goat's milk.
Life is not all doom and gloom. With care, I can still have an evening meal and drink a small bottle of retsina in a local taverna for less than 15 euros.
But we do not buy fish in restaurants anymore. Instead, we take our own to be cooked and shared with whomever is around.
The Greek newspapers say this is a bumper year for tourism, but there were spare beds in the village even in August and in September the place is empty - there are more tavernas than tourists.
We still have day trippers from the south but they are on the lower end of the social scale and have little money to spend. Some bring their own sandwiches.
Earlier in the year, the fishermen from Kalymnos were ordered to stop fishing as there was no market in Rhodes for the catch.
The large hotels import squid from Thailand and undersized red mullet from Morocco and the smaller restaurants could not attract enough customers.
We still get the super-rich in their gin palaces. They buy bread from the little shop, drink an ouzo or two, and head back to their bunks to sleep it off.
They are welcome, of course, but there is little evidence of any trickle-down effect.
European newspapers like to blame the Greeks for the crisis but when the man in the taverna, or the woman queuing for vegetables, say they did not cause the problem, it is hard to disagree.
Roger Jinkinson's earlier dispatch from Karpathos looked at the island's traditions of solidarity and endurance. He is the author of Tales from a Greek Island

The 2011 deficit is projected to be 8.5% of GDP, down from 10.5% in 2010 but short of the 7.6% target.
The government, which on Sunday adopted its 2012 draft budget, blamed the shortfall on deepening recession.
The figures come as inspectors from the IMF, EU and European Central Bank are in Athens to decide whether Greece should get a key bail-out instalment.
Greece needs the 8bn euros (£6.9bn; $10.9bn) instalment to avoid going bankrupt next month.
Bankruptcy would put severe pressure on the eurozone, damage European bank finances and possibly have a serious knock-on effect on the world economy.
'Unanimously approved' The Greek finance ministry said on Sunday that its unpopular austerity measures would have to be adhered to even if the latest targets were to be met.
It said: "Three critical months remain to finish 2011, and the final estimate of 8.5% of GDP deficit can be achieved if the state mechanism and citizens respond accordingly."
It released figures for 2012's projected deficit, putting it at 6.8% of GDP, also short of the 6.5% target.
The figures came as the government met to approve Greece's draft budget for next year.
It blamed an economic contraction this year of 5.5% - rather than May's 3.8% estimate - for the failure to meet deficit targets.
The cabinet meeting also approved a measure to put 30,000 civil service staff on "labour reserve" by the end of the year.
This places them on partial pay with possible dismissal after a year.
"The labour reserve measure was approved unanimously," one deputy minister told Reuters.
This measure, along with other wage cuts and tax rises, have been part of a package intended to persuade the so called "troika" of the EU, IMF and ECB to continue with its bail-out.
The inspectors will report back to EU finance ministers soon but analysts believe they have little choice but to approve the latest tranche.
The Greek austerity measures are hugely unpopular at home and have led to a wave of strikes and protests.
Many Greeks believe the austerity measures are strangling any chance of growth.

Mr Perry was speaking during a campaign appearance in New Hampshire.
"It may require our military in Mexico working in concert with them to kill these drug cartels and keep them off our border," he said.
Such a move would go far beyond current US involvement in Mexico's drugs war.
The suggestion is also likely to irritate Mexico's government over the sensitive issue, correspondents say.
Governor Perry gave no further details of what sort of possible military intervention he would consider.
"I don't know all the different scenarios that would be out there," he said.
"But I think it is very important for us to work with them to keep that country from failing".
Sovereignty After the speech, the White House said it would continue its "historic level of cooperation with Mexico" to protect people on both sides of the border.
The Obama administration currently provides substantial material support to Mexican security forces, as well as close intelligence cooperation.
The US has also deployed National Guard troops to boost border security, and uses pilotless drone aircraft to gather intelligence inside Mexico.
Any deployment of US military forces on Mexican territory would almost certainly be unacceptable to the Mexican authorities.
Mexico lost around half its territory to the US after a war in the 1840s, and has since been very protective of its sovereignty.
The Mexican constitution also places strict limits on foreign intervention.
Mexican President Felipe Calderon has been pressing the US to do more to reduce demand for drugs among its citizens and to reduce the flow of weapons from the US to the cartels.
Correspondents say Mr Perry's comments may be aimed at showing he is tough on border security and illegal immigration - issues on which he has been attacked by other contenders for the Republican nomination.

Speaking to the BBC's Andrew Marr Show, he said the debt crisis in the eurozone was "a threat not just to itself, but also a threat to the UK economy, and a threat to the world economy".
He reiterated that eurozone leaders had to take quick and decisive action.
Mr Cameron said that, as 40% of UK exports went to the eurozone, it could not shield itself from the problem.
The prime minister said the UK government had "a very clear view" of what needed to be done, and that it was pushing this with its partners in Europe and the International Monetary Fund (IMF).
He said eurozone leaders had to strengthen the region's financial mechanisms, ensure the greater involvement of the IMF, and deal decisively with the high levels of sovereign debt.
Mr Cameron added: "Action needs to be taken in the next coming weeks to strengthen Europe's banks, to build the defences that the eurozone has, to deal with the problems of debts decisively."
He said these emergency measures were needed before any long-term plans of more economic coordination across the eurozone were introduced, such as a single tax system.
Greek fears European stock markets again fell heavily on Friday due to concerns about the debt crisis in the eurozone.
The concerns centre on Greece, the most indebted eurozone nation.
Greece needs its next 8bn euros (£6.9bn; $10.9bn) instalment of European Union (EU) and International Monetary Fund (IMF) bailout loans by the middle of this month to be able to continue paying its civil servants and teachers.
This tranche was delayed in September after EU, IMF and European Central Bank officials said the Greek government was not carrying out sufficient austerity measures.
The wider fear is that Greece will ultimately default on its debt payments, and of the knock-on effect this would have on banks across Europe which own Greek government bonds.
Some commentators also warn that Greece may ultimately have to leave the eurozone, plunging the region's economic and political systems into chaos.
Eurozone leaders and the IMF are now continuing to work on a solution to the debt crisis, with French President Nicolas Sarkozy and German Chancellor Angela Merkel due to speak again this week.

They were part of a larger group crossing the bridge from Manhattan, where they have been camped out near Wall Street for two weeks.
Some entered the bridge's roadway and were met by a large police presence and detained, most for disorderly conduct.
The loosely-organised group is protesting against corporate greed.
They say they are defending 99% of the US population against the wealthiest 1%.
Occupy Wall Street called for 20,000 people to "flood into lower Manhattan" on 17 September and remain there for "a few months".
Several hundred remain camped at Zuccotti Park, a privately owned area of land not far from Wall Street.
A police spokesman quoted by Reuters said the arrests came "after multiple warnings by police were given to protesters to stay on the pedestrian walkway".
"Some complied and took the walkway without being arrested. Others locked arms and proceeded on the Brooklyn-bound vehicular roadway. The latter were arrested," the spokesman said.
Many were released again shortly afterwards, police said.
Some of the protesters said police had allowed them on to the roadway and were escorting them across when they were surrounded and the arrests began.
"This was not a protest against the NYPD. This was a protest of the 99% against the disproportionate power of the 1%," protester Robert Cammiso told the BBC.
"We are not anarchists. We are not hooligans. I am a 48-year-old man. The top 1% control 50% of the wealth in the USA."
Another protester, Henry-James Ferry, said: "It is not fair that our government supports large corporations rather than the people.
"I only heard about the protest on day one when I came across it. I then decided to go back every day," he told the BBC.
March on police HQ The protesters have had previous run-ins with New York's police.
On Friday, about 2,000 people marched under the Occupy Wall Street banner to New York's police headquarters to protest against arrests and police behaviour.
Some 80 people were arrested during a march on 25 September, mostly for disorderly conduct and blocking traffic, but one person was charged with assaulting a police officer.
A series of other small-scale protests have also sprung up in other US cities in sympathy with the aims of Occupy Wall Street.

The Evelyn Grace Academy in Brixton, designed by Zaha Hadid Architects, has been given the Royal Institute of British Architects' Stirling Prize.
It beat the favourite, the London 2012 Olympic velodrome. Hadid has now won the Stirling for two years in a row.
The prize is awarded to the best new European building that has been built or designed in Britain.
The other nominated buildings included the renovated Royal Shakespeare Theatre in Stratford-upon-Avon and the Folkwang Museum in Essen, Germany.
The Royal Institute of British Architects (Riba) described the £37.5m academy as a "highly stylized zig-zag of steel and glass".
Riba president Angela Brady, who chaired the judging panel, praised the way the "imaginative" design was "expertly inserted into an extremely tight site".
The architects had to accommodate four schools under a single academy umbrella.
With a relatively small location and sport as one of the academy's "special subjects", they put a 100-metre running track through the middle of the site, under a bridge between two school blocks.
"The Evelyn Grace Academy is an exceptional example of what can be achieved when we invest carefully in a well-designed new school building," Ms Brady said.
The annual award is given to the architects of the building that has "made the greatest contribution to the evolution of architecture in the past year".
Zaha Hadid's London-based practice won for the Maxxi contemporary art museum in Rome last year.
The consecutive victories confirm her as one of the country's leading architects, with the London 2012 Olympic Aquatics Centre, Glasgow's Riverside Museum and plans for the Cardiff Bay Opera House also to her name.
Hadid grew up in Iraq before leaving at the age of 17. She has not been back to the country for 30 years but will soon return to design Baghdad's Central Bank - a prospect she describes as "very emotional".

She said she believed that architecture could have an impact on behaviour and education.
"I think there's no question that the environment impacts on everybody, whether it's schooling or housing or hospitals," she said. "Wellbeing and architecture are connected, there's no question about it."
Discussing the philosophy behind her projects, she added: "The most important thing is to inspire people. And that's why schooling and education is the most important [thing]."
The academy's principal Peter Walker said students were positive about the building and that it may inspire them to go on to great things. But he added that a beautiful building was of no benefit unless the education was up to scratch.
"High standards of behaviour and very high aspirations in terms of academic achievement are at the heart of what we're about, and having an aspirational building supports that drive," he said.
"I'm sure there are students who will be inspired to look at design and perhaps at architecture through attending the building, but fundamentally they won't get there unless what we provide in our classrooms is of high quality for their learning."
Hadid, who will receive a cheque for £20,000, was in the US and so missed the ceremony at the Magna Science Adventure Centre in Rotherham, which won the prize in 2001.
The other shortlisted buildings were An Gaelaras, a cultural centre in Derry, and The Angel Building, a renovated 1980s office block in Islington, London.
The prize was set up in 1996 and is named after the late British architect Sir James Stirling.
The ceremony will be broadcast on The Culture Show on BBC Two on Sunday.

The bombing on Saturday evening hit 119th brigade troops near Zinjibar in restive Abyan province and was followed by attacks by militants, reports say.
It is unclear how many died in the actual bombing, or if it was an error.
However, Yemeni TV said no such air strike had taken place.
Reports say the 119th brigade has joined a rebellion against President Ali Abdullah Saleh.
The militants, allegedly linked to al-Qaeda, have exploited the chaos brought by months of anti-government protests to step up activities in the area.
The army is fighting to regain lost territory and took Zinjibar back from the militants last month.
At least 26 troops and militants died in fighting in the area on Saturday.
Opposition groups say Yemen's government has played up the al-Qaeda threat in an effort to boost international support.
Sanaa gunfire Local residents told the BBC the plane had hit an abandoned school where the troops were taking shelter, and medical sources at a hospital in the province said they had received a number of dead bodies.
A military official told AFP that militants later attacked the base and "killed even more soldiers".
The Red Crescent confirmed that 30 had died but was unable to say how they were killed.
Violence raging in the south has sparked fears of a humanitarian crisis in the Gulf Arab republic, which has been on the brink of civil war since some military units and tribal groups joined anti-government protests in recent months.
Protesters rallied in Sanaa on Sunday to demand the removal of President Saleh, who has refused to step down despite international pressure. Hundreds of people have been killed since protests began in January.
There were also reports of gunfire near the base of rebel Gen Ali Mohsen.
Mr Saleh returned to the country more than a week ago after months of treatment in Saudi Arabia for injuries sustained when his residence was bombed.
The latest incident in the south comes days after the killing of US-born Islamist cleric Anwar al-Awlaki by a suspected US drone in the east of the country.
Seen as a key figure in al-Qaeda in the Arabian Peninsula, Awlaki had been on the run in Yemen since December 2007.

After a two-day meeting, leaders said the Syrian National Council (SNC) was aiming to bring about a new, democratic Syria and was open to all citizens.
The council was created last month in an attempt to unite opponents of President Bashar al-Assad.
Meanwhile, government troops have retaken the central town of Rastan.
The town of 40,000, in the restive province of Homs, has seen days of fierce fighting between Mr Assad's forces and army defectors who refused to fire on protesters.
At least 2,700 people are believed to have been killed in six months of protests against Mr Assad, who has refused to step down.
'Struggle for liberty' "The Syrian National Council reunites the forces of the opposition and the peaceful revolution," Burhan Ghalioun, who had earlier been named as chairman, told AFP news agency.
"It is an independent group personifying the sovereignty of the Syrian people in their struggle for liberty.
"The council rejects any outside interference that undermines the sovereignty of the Syrian people," he added.
Mr Ghalioun, a France-based academic, was named last month as the leader of the council, which has Islamist and nationalist supporters and includes the Local Coordination Committees, which organises activists on the ground.
Mr Ghalioun added that the SNC would allow "a united direction to face up to the daily massacres of civilians by the regime, especially in Rastan."
On Sunday, activists and state TV said government troops now had full control of Rastan, 160km (100 miles) north of Damascus.
Activists said the government had sent in 250 tanks and armoured vehicles in an attempt to suppress the revolt, and that 50 of those vehicles left on Sunday.
"Many houses have been destroyed there and the humanitarian situation is very bad," the UK-based Syrian Observatory for Human Rights said.
"We have information that dozens of civilians were killed and buried in the gardens of houses as the army shelled the town," it added, according to AP news agency.
Foreign journalists are restricted from operating freely in Syria and reports cannot be independent verified.
Army deserters said in a statement they had been forced to retreat.
"Because of major reinforcements and the weapons used in Rastan by Assad's gangs... we have decided to withdraw in order to better wage the struggle for liberty," the statement said.
State news agency Sana reported that "stability and calm have been restored" in the town and that life had returned to normal.

Hundreds of residents, in vehicles packed with belongings, are queuing at checkpoints leading out of the city.
Transitional authority forces say they are observing a truce to encourage the remaining civilians to get out, before launching a final assault.
Meanwhile, an International Red Cross team has been into Sirte and says there is an urgent need for medical aid.
Sirte is one of two major cities still holding out against the National Transitional Council (NTC) forces.
The whereabouts of Col Gaddafi remain unknown.
War-wounded kits Scores of cars, buses and trucks piled high with household goods were lined up at NTC checkpoints on the outskirts of Sirte on Sunday.
The fleeing residents said the situation in the city had deteriorated to such an extent that there was little food and no water or electricity.
Another man, Ali, said he and his family were leaving because "we are caught between Nato bombings and shelling by rebels".
"Nato, in particular, is bombing at random and is often hitting civilian buildings," he told the AFP news agency.
The Geneva-based ICRC says nearly 10,000 people have now left Sirte, with at least a third setting up camp in desert areas just a few kilometres from the city not wishing to travel too far from their homes.
It says that in Sirte itself, people are dying in the main hospital because of a shortage of oxygen and fuel.
An ICRC team was given security clearance from both sides to cross checkpoints and visit the city's Ibn Sima hospital on Saturday.
"The hospital is facing a huge influx of patients, medical supplies are running out and there is a desperate need for oxygen. On top of that, the water reservoir has been damaged," the ICRC said in a statement.
The team was able to pass through the front lines and deliver medical equipment.
"What we have delivered is war wounded kits, I mean, basically this is medical equipment in order to be able to carry out operations for war wounded, about 200 war wounded patients," spokeswoman Soaade Messoudi told the BBC.
However, the team could not visit wounded people on the wards as the hospital came under fire.
"Several rockets landed within the hospital buildings while we were there," the leader of the ICRC team, Hichem Khadhraoui, told AFP.
"We saw a lot of indiscriminate fire. I don't know where it was coming from," Mr Khadhraoui said.
Gaddafi loyalists have been putting up stiff resistance in Sirte since NTC troops began their assault several weeks ago.
On Friday, the NTC troops captured the airport. Forces from the east and west of the country are moving against the city and are trying to launch co-ordinated attacks against the Gaddafi loyalists in the city centre.
Only when they have taken it will they consider Libya to be fully under their control, says the BBC's Jonathan Head on the outskirts of the city.
Bani Walid is the only other remaining centre of resistance against NTC forces.